Liquid crystal display device having pixels with memories

ABSTRACT

A liquid crystal display device includes: a display unit configured to pixels in a display region, a pixel drive circuit configured to apply voltage to liquid crystals, a memory configured to store therein a setting signal indicating whether to apply voltage to the liquid crystals in the display region, and two switch elements for switching coupling with the pixel drive circuit; and a controller configured to rewrite the setting signal stored in the memory when a mode in which the display unit is operated is switched, between a first mode causing the display unit to perform display output in accordance with a gradation signal generated based on image data, and a second mode causing the display unit to perform display output in accordance with the setting signal stored in the memory.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Application No.2015-209034, filed on Oct. 23, 2015, the contents of which areincorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present invention relates to a liquid crystal display device.

2. Description of the Related Art

A conventionally known liquid crystal display device performs display bysupplying potential that a digital memory element holds to a liquidcrystal cell of a pixel (for example, Japanese Patent ApplicationLaid-open Publication No. 2011-118307 A). Such a display output methodusing what is called a memory function tends to be superior in powersaving capability compared to a display output method of updatingvoltage applied to the liquid crystal cell in accordance with agradation signal in each frame.

A digital memory element disclosed in Patent Literature 1 can switchonly the turning on and off of the pixel, but cannot have gradationcapability in three values or more. However, higher gradation output hasbeen desired in response to requirements for the liquid crystal displaydevice having the memory function.

The present invention intends to solve the above-described problem, andit is an object thereof to provide a liquid crystal display device thatcan achieve the memory function and a display output function havinggradation capability at two values or more. It is another object of thepresent invention to provide a liquid crystal display device that canperform switching between display output using the memory function anddisplay output using gradation capability at two values or more.

SUMMARY

A liquid crystal display device according to one aspect includes adisplay unit configured to pixels in a display region, a pixel drivecircuit configured to apply voltage to liquid crystals, a memoryconfigured to store therein a setting signal at least in one bitindicating whether to apply voltage to the liquid crystals in thedisplay region, and two switch elements of a first switch and a secondswitch for switching coupling with the pixel drive circuit, and acontroller configured to rewrite the setting signal stored in the memorywhen a mode in which the display unit is operated is switched, between afirst mode causing the display unit to perform display output inaccordance with a gradation signal generated based on image data in thecase of turning on one of the two switch elements, and a second modecausing the display unit to perform display output in accordance withthe setting signal stored in the memory in the case of turning on anyone of the two switch elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an exemplary configuration of a liquidcrystal display device according to a first embodiment of the presentinvention;

FIG. 2 is a sectional view schematically illustrating the structure of adisplay unit according to the first embodiment;

FIG. 3 is a diagram illustrating an exemplary relation among a unitpixel, sub pixels included in the unit pixel, and pixels included ineach sub pixel in the first embodiment;

FIG. 4 is a diagram illustrating an exemplary ON/OFF pattern of threepixels included in a sub pixel;

FIG. 5 is a diagram illustrating an exemplary schematic configuration ofa pixel drive circuit and an MIP circuit;

FIG. 6 is a diagram illustrating the process of mode change after theliquid crystal display device is turned on;

FIG. 7 is a diagram illustrating an operation state of each component ofthe pixel drive circuit and the MIP circuit before the liquid crystaldisplay device changes to WMA or WMM after being turned on;

FIG. 8 is a timing chart schematically illustrating the potentials of asignal line, a counter electrode, a scanning line, a second scanningline, and a wire before the liquid crystal display device changes to WMAor WMM after being turned on;

FIG. 9 is a diagram illustrating the operation state of each componentof the pixel drive circuit and the MIP circuit in WMA;

FIG. 10 is a timing chart schematically illustrating the potentials ofthe signal line, the counter electrode, the first scanning line, thesecond scanning line, and the wire in WMA;

FIG. 11 is a diagram illustrating the operation state of each componentof the pixel drive circuit and the MIP circuit in AM;

FIG. 12 is a timing chart schematically illustrating the potentials ofthe signal line, the counter electrode, the first scanning line, thesecond scanning line, and the wire in AM;

FIG. 13 is a diagram illustrating the operation state of each componentof the pixel drive circuit and the MIP circuit in WMM;

FIG. 14 is a timing chart schematically illustrating the potentials ofthe signal line, the counter electrode, the first scanning line, thesecond scanning line, and the wire in WMM;

FIG. 15 is a diagram illustrating the operation state of each componentof the pixel drive circuit and the MIP circuit in MM;

FIG. 16 is a timing chart schematically illustrating the potentials ofthe signal line, the counter electrode, the first scanning line, thesecond scanning line, and the wire in MM;

FIG. 17 is a timing chart illustrating a relation among a mode of theliquid crystal display device, a signal output to the signal line, asignal output to the counter electrode, and whether to perform displayoutput by the display unit in the first embodiment;

FIG. 18 is a timing chart illustrating the relation among the mode ofthe liquid crystal display device, the signal output to the signal line,the signal output to the counter electrode, and whether to performdisplay output by the display unit in the first embodiment;

FIG. 19 is a timing chart illustrating the relation among the mode ofthe liquid crystal display device, the signal output to the signal line,the signal output to the counter electrode, and whether to performdisplay output by the display unit in the first embodiment;

FIG. 20 is a timing chart illustrating an exemplary potential change inresponse to signal output related to one unit pixel in 1H duration inWMA;

FIG. 21 is a timing chart illustrating an exemplary potential change inresponse to signal output related to one unit pixel in 1H duration inAM;

FIG. 22 is a timing chart illustrating an exemplary potential change inresponse to signal output related to one unit pixel 1H duration in WMM;

FIG. 23 is a timing chart illustrating an exemplary potential change inresponse to signal output related to one unit pixel in 1H duration inMM;

FIG. 24 is a schematic diagram illustrating exemplary setting ofdurations that are included in 1H and can be used as WMA, AM, and WMM;

FIG. 25 is a timing chart illustrating exemplary signal output in 1H inthe first frame during an AM operation;

FIG. 26 is a timing chart illustrating exemplary signal output in 1H inthe second frame or later the AM operation;

FIG. 27 is a timing chart illustrating exemplary signal output in 1H inthe first frame during a MM operation;

FIG. 28 is a timing chart illustrating exemplary signal output in 1H inthe second frame or later during the MM operation;

FIG. 29 is a diagram illustrating the process of a mode change of theliquid crystal display device in a second embodiment;

FIG. 30 is a schematic diagram illustrating an exemplary laminatedstructure of a liquid crystal display device according to a thirdembodiment;

FIG. 31 is an exploded perspective view illustrating an exemplary mainconfiguration of a touch detecting unit;

FIG. 32 is a timing chart illustrating an exemplary relation betweensignal output and a touch detection duration in 1H in the first frameduring the AM operation;

FIG. 33 is a timing chart illustrating an exemplary relation between thesignal output and the touch detection duration in 1H in the second frameor later the AM operation;

FIG. 34 is a timing chart illustrating an exemplary relation between thesignal output and the touch detection duration in 1H in the first frameduring the MM operation;

FIG. 35 is a timing chart illustrating an exemplary relation between thesignal output and the touch detection duration in 1H in the second frameor later during the MM operation; and

FIG. 36 is a diagram illustrating another exemplary relation amongdurations that are included in 1H and can be used as WMA, AM, and WMM,and the touch detection duration.

DETAILED DESCRIPTION

Embodiments of to the present invention will be described below withreference to the accompanying drawings. The present disclosure is merelyexemplary, and thus the present invention includes any modification thatcould be easily thought of by the skilled person in the art asappropriate without departing from the scope of the invention. Somedrawings schematically illustrate the width, thickness, shape, and thelike of each component differently from the actual aspect for clearerdescription, but are merely exemplary and do not limit theinterpretation of the present invention. In the present specificationand the drawings, any element same as that described with reference toan already described drawing is denoted by the same reference numeralsand symbols, and detailed description thereof will be omitted asappropriate in some cases.

First Embodiment

FIG. 1 is a diagram illustrating an exemplary configuration of a liquidcrystal display device according to a first embodiment of the presentinvention. FIG. 2 is a block diagram of an exemplary configuration of aliquid crystal display device 1 according to the first embodiment. Theliquid crystal display device 1 includes a display unit 10 and a controlunit 20. The liquid crystal display device 1 displays an image byreflecting external light through the display unit 10. Specifically, forexample, as illustrated in FIG. 1, the liquid crystal display device 1includes the display unit 10 that includes a display panel 40 on which aplurality of unit pixels 48 are provided in a matrix along row andcolumn directions, and the control unit 20 that is a circuit configuredto perform various kinds of control related to display outputting by thedisplay unit 10 through a LCD driver 30 configured to operate a pixel 49(refer to FIG. 2) included in each unit pixel 48 of the display panel40. The liquid crystal display device 1 includes an externally extendedFPC, and is capable of performing display in accordance with image dataoutput from an external device coupled through the FPC. The liquidcrystal display device 1 according to the first embodiment is areflective liquid crystal display device, but may be a transmissive ortransflective liquid crystal display device.

FIG. 2 is a sectional view schematically illustrating the structure ofthe display unit 10 according to the first embodiment. As illustrated inFIG. 2, the display unit 10 includes a pixel substrate 41 and a countersubstrate 42, both facing each other, and a liquid crystal layer 43provided between the pixel substrate 41 and the counter substrate 42 andencapsulating liquid crystal elements.

The pixel substrate 41 is provided with a plurality of pixel electrodes44 on one of its surfaces closer to the liquid crystal layer 43. Eachpixel electrode 44 is coupled with a signal line DTL through a switchingelement, and receives application of a gradation signal as an imagesignal or a one-bit signal as a setting signal. The pixel electrode 44is, for example, a reflective member made of aluminum or silver, andreflects external light. In other words, in the first embodiment, eachpixel electrode 44 serves as a reflective unit that displays an image byreflecting light entering through a front surface as a display surfaceof the display unit 10. The reflective unit may be formed as any layerthat is different from the pixel electrodes 44 as long as the reflectiveunit is arranged closer to the pixel substrate 41 than the liquidcrystal layer 43. In this case, the pixel electrodes 44 may be formed ofa transparent conductive material such as indium tin oxide (ITO) insteadof a reflective material. The pixel substrate may be provided with apolarization plate on the other of its surfaces farther from the liquidcrystal layer 43.

The counter substrate 42 is a transparent substrate made of, forexample, glass. The counter substrate 42 includes a counter electrode45, a color filter 46, a polarization plate 47, and a light guidingplate 55. The color filter 46 may be formed on the pixel substrate 41.

The counter electrode 45 is made of a transparent conductive materialsuch as ITO or indium zinc oxide (IZO). The counter electrode 45 iscoupled with the switching element coupled with each pixel electrode 44.The pixel electrode 44 and the counter electrode 45 are provided facingeach other, and thus the pixel electrode 44 and the counter electrode 45generate an electric field in the liquid crystal layer 43 when voltageis applied therebetween by the gradation signal. The electric fieldgenerated in the liquid crystal layer 43 twists the liquid crystalelements and changes a birefringence index. This allows the liquidcrystal display device 1 to adjust the quantity of light reflected bythe display unit 10. The display unit 10 in the first embodiment is whatis called a vertical electric-field type, but may be a horizontalelectric-field type in which an electric field is generated in adirection parallel to the display surface of the display unit 10. Morespecifically, the counter electrode 45 may be provided on the pixelsubstrate 41, and arranged above, within, or below the pixel electrode44 through an insulating layer. The counter electrode 45 may be made ofa reflective material and have a function as a reflective unit.

The color filters 46 is provided for each pixel electrode 44. Thecounter substrate 42 is provided with the polarization plate 47 and thelight guiding plate 55 on one of its surfaces farther from the liquidcrystal layer 43. The polarization plate 47 is a transparent plate orfilm made of, for example, cellulose triacetate (TAC) resin or polyvinylalcohol (PVA) resin. The polarization plate 47 adjusts the polarizationangles of external light LO1 entering from the outside of the displaypanel 40 and light LO2 emitted from the display panel 40. The lightguiding plate 55 is a transparent plate made of, for example, acrylicresin, polycarbonate (PC) resin, or methyl-methacrylate-styrenecopolymer (MS resin). The light guiding plate 55 is provided with prismfabrication on one of its surfaces (upper surface) farther from thecounter substrate 42. The light guiding plate 55 adjusts the directionsof the external light LO1 entering from the outside of the display panel40 and the light LO2 emitted from the display panel 40.

The following describes reflection of light by the display unit 10. Asillustrated in FIG. 2, the external light LO1 is incident on the displaypanel 40. The external light LO1 is incident on the pixel electrodes 44through, for example, the light guiding plate 55, the polarization plate47, the counter substrate 42, and the color filter 46. The externallight LO1 incident on the pixel electrodes 44 is reflected by the pixelelectrodes 44 and externally emitted as the light LO2.

In other words, each pixel electrode 44 externally reflects the externallight LO1 incident on the display unit 10 through the front surface ofthe display unit 10. The externally reflected light LO2 passes throughthe liquid crystal layer 43 and the color filter 46. Accordingly, theliquid crystal display device 1 can display an image by the externallyreflected light LO2. With this configuration, the liquid crystal displaydevice 1 according to the first embodiment is a reflective liquidcrystal display device.

FIG. 3 is a diagram illustrating an exemplary relation among each unitpixel 48 in the first embodiment, a sub pixel included in the unit pixel48, and the pixel 49 included in the sub pixel. The display unit 10includes a plurality of the unit pixels 48 arranged in the row andcolumn directions. As illustrated in FIG. 3, one unit pixel 48 includesa plurality of the sub pixels. Each sub pixel is provided with the colorfilter 46 of a different color. One unit pixel 48 in the firstembodiment includes three sub pixels. A combination of colors of thecolor filters 46 provided to the three sub pixels are red (R), green(G), and blue (B). This number of sub pixels and this combination ofcolors are merely exemplary, and may be modified as appropriate. In FIG.3, a sub pixel provided with the color filter 46 of red (R) is denotedby reference numeral 49R. A sub pixel provided with the color filter 46of green (G) is denoted by reference numeral 49G. A sub pixel providedwith the color filter 46 of blue (B) is denoted by reference numeral49B.

One sub pixel includes a plurality of (for example, three) the pixels49. The plurality of the pixels 49 provided in the sub pixel serve asindividually controlled minimum units. Each sub pixel according to thefirst embodiment has a function to perform outputting in three-bit areacoverage modulation through an ON/OFF pattern of a pixel 49 a, a pixel49 b, and a pixel 49 c, the three pixels having different sizes ofdisplay regions. Each display region is a region through which light istransmitted in accordance with a voltage applied to liquid crystals inthe liquid crystal layer 43. The pixel 49 a, the pixel 49 b, and thepixel 49 c are collectively referred to as the pixel 49 when the threepixels are not needed to be distinguished. For example, a displaymechanism is the same between the pixel 49 a, the pixel 49 b, and thepixel 49 c, and thus the pixel 49 is illustrated in FIG. 2. The pixel 49a, the pixel 49 b, the pixel 49 c each achieve a different displayregion through a different area of the pixel electrode 44 or differentareas of the pixel electrode 44 and the counter electrode 45. The “pixel49” refers to any one of a plurality of the pixels 49 a, 49 b, and 49 cincluded in a sub pixel.

FIG. 4 is a diagram illustrating an exemplary ON/OFF pattern of threepixels 49 included in a sub pixel. In FIG. 4, shading is provided to anypixel 49 in a non-transmissive state. As illustrated in FIG. 4, the subpixel according to the first embodiment can perform outputtingcorresponding to three-bit (eight) gradation values through combinationsof transmission (ON) and non-transmission (OFF) of each of the threepixels 49. The transmission (ON) refers to, for example, a state inwhich the pixel 49 is performing outputting at a highest gradation. Thenon-transmission (OFF) refers to, for example, a state in which thepixel 49 performs outputting at a lowest gradation. Outputting at thetransmission is not limited to the highest gradation, but may be agradation higher than that at the non-transmission.

The outputting corresponding to the three-bit gradation values describedwith reference to FIG. 4 is achieved by switching the transmission (ON)and non-transmission (OFF) of the pixel 49, but the pixel 49 accordingto the first embodiment can perform outputting at multiple gradationsirrespective of the switching of the transmission (ON) andnon-transmission (OFF). When each pixel 49 performs the multiplegradation outputting, one sub pixel in the first embodiment can performthe multiple gradation outputting in, for example, 18 bits. Accordingly,the gradation capability of the sub pixel depends on gradationcapability of the pixel 49.

In the first embodiment, the three pixels 49 included in one sub pixelhave different sizes of display regions, but this is merely exemplaryand the present invention is not limited thereto. Part or all of aplurality of pixels 49 included in one sub pixel may have identicalshapes and sizes of display regions.

The number of the pixels 49 included in each sub pixel is not limited tothe example described with reference to FIG. 4 but is optional. Thenumber of bits for the area coverage modulation depends on, for example,the number of the pixels 49 included in one sub pixel and the size ofthe display region of each of the pixels 49.

FIG. 5 is a diagram illustrating an exemplary schematic configuration ofa pixel drive circuit 50 and a memory-in-pixel (MIP) circuit 60. Theschematic configuration of the pixel drive circuit 50 and the MIPcircuit 60 is common between all pixels 49 irrespective of the sizes ofthe display regions of the pixels 49. As illustrated in FIGS. 2 and 5,one pixel 49 includes the pixel drive circuit 50 and the MIP circuit 60provided between the pixel electrode 44 and the pixel substrate 41.

The pixel drive circuit 50 applies voltage to the liquid crystals of theliquid crystal layer 43 in the display region. Specifically, the pixeldrive circuit 50 includes for example, a couple wire coupled with thepixel electrode 44, and a thin film transistor (TFT) 51 provided to thiscouple wire and configured to operate in response to a drive signaltransmitted through a first scanning line SCL. The couple wire iscoupled with one of the signal line DTL and the counter electrode 45through selection wire. When the TFT 51 is turned on in response to adrive signal while the couple wire and the signal line DTL are coupledwith each other through the selection wire, a signal such as thegradation signal transmitted through the signal line DTL is applied tothe pixel electrode 44. Accordingly, voltage in accordance with thesignal is applied between the pixel electrode 44 and the counterelectrode 45. When the TFT 51 is turned on in response to a drive signalwhile the couple wire and the counter electrode 45 are coupled with eachother through the selection wire, the pixel electrode 44 and the counterelectrode 45 are electrically coupled with each other, and thus thepixel electrode 44 and the counter electrode 45 have identicalpotentials, and the voltage between the pixel electrode 44 and thecounter electrode 45 becomes zero. In the first embodiment, when thevoltage between the pixel electrode 44 and the counter electrode 45becomes zero, the pixel 49 is turned off.

The TFT 51 illustrated in, for example, FIG. 5 is provided to be adouble gate type, but is not limited thereto and may be a single gatetype.

The selection wire includes a first bifurcating line coupling the couplewire and the signal line DTL, a second bifurcating line coupling thecouple wire and the counter electrode 45, and TFTs 71 and 72 provided toeach of the first bifurcating line and the second bifurcating line. Thefirst bifurcating line couples the signal line DTL and the couple wirewhile the TFT 71 is turned on. The second bifurcating line couples thecounter electrode 45 and the couple wire while the TFT 72 is turned on.

The MIP circuit 60 serves as a memory in the first embodiment.Specifically, the MIP circuit 60 includes a latch circuit holding aone-bit signal, a wire coupling this latch circuit and the signal lineDTL, and a TFT 81 provided to this wire and configured to operate inresponse to a latch update signal transmitted through a second scanningline SCLM.

The latch circuit is coupled with a wire VSS being at a predeterminedground potential (GND potential) and a wire VRAM to which a signal at aVGH potential or a VDD potential output from an oscillator included inthe control unit 20 is applied. The VGH potential is higher than the VDDpotential and the GND potential. The VDD potential is higher than theGND potential. When the VGH potential is applied through the wire VRAM,the latch circuit continues holding the one-bit signal.

The latch circuit turns on one of the TFT 71 and the TFT 72 and turnsoff the other depending on a held value. The value held by the latchcircuit in the first embodiment is represented by Low (0) or High (1).The TFT 71 is turned on when the value is Low, whereas the TFT 72 isturned on when the value is High. Hereinafter, the simple notation of“Low” or “High” indicates the value held by the latch circuit. In a caseof Low, the couple wire is coupled with the signal line DTL. In a caseof High, the couple wire is coupled with the counter electrode 45.

The control unit 20 is an integrated circuit (IC) as an integration of,for example, a power circuit, an oscillator, a timing controller, animage memory, an interface control circuit, and a panel control circuit.The power circuit supplies the VGH potential, the VDD potential, and theGND potential. The oscillator supplies alternating current used in, forexample, inversion drive. The timing controller T-CON outputs a clocksignal. The interface control circuit generates the gradation signal andthe one-bit signal to be input to each pixel 49 of the display unit 10based on an image signal input through a flexible printed board (FPC)from a control device included in an electronic apparatus with theliquid crystal display device 1. The panel control circuit outputsvarious kinds of control signals by which the display unit 10 isoperated in any one of an analog mode (AM) and a memory mode (MM)depending on a mode specifying signal. The mode specifying signaldetermines an operation mode of the liquid crystal display device 1 andis output by an external control device to be described later. Thesimple notations of “AM” and “MM” indicate “the analog mode” and “thememory mode”, respectively. AM is a mode in which the display unit 10performs display output in accordance with the gradation signalgenerated based on image data. MM is a mode in which the display unit 10performs display output in accordance with the one-bit signal held inthe memory (MIP circuit 60).

The control unit 20 is coupled with an X driver 32 and a Y driver 31included in the LCD driver 30. The control unit 20 controls operationstates of the pixel drive circuit 50 and the MIP circuit 60 byoutputting signals to the first scanning line SCL and the secondscanning line SCLM through the X driver 32. The control unit 20 alsocontrols the gradation of each pixel 49 by outputting the gradationsignal or the one-bit signal to the signal line DTL through the Y driver31. The X driver 32 is a circuit configured to output a drive signal tothe first scanning line SCL and the latch update signal to the secondscanning line SCLM under control of the control unit 20. The Y driver 31is a circuit configured to output the gradation signal or the one-bitsignal to the signal line DTL coupled with each pixel 49 under controlof the control unit 20.

The control unit 20 according to the first embodiment includes a memoryconfigured to store therein information on start-up setting (AM or MM).The start-up setting is set in accordance with the mode specifyingsignal.

The following describes the mode switching of the display unit 10. Thedisplay unit 10 operates in AM as a first mode or MM as a second mode.The control unit 20 performs first mode preparation processing (WriteMode A: WMA) in advance to operate the display unit 10 in AM. Thecontrol unit 20 performs second mode preparation processing (Write ModeM: WMM) in advance to operate the display unit 10 in the memory mode.The simple notations of “WMA” and “WMM” indicate “the first modepreparation processing” and “the second mode preparation processing”,respectively.

FIG. 6 is a diagram illustrating the process of a mode change of theliquid crystal display device 1. The liquid crystal display device 1changes to WMM or WMA after being turned on. The liquid crystal displaydevice 1 changes to AM through WMA after being turned on. The liquidcrystal display device 1 also changes to MM through WMM after beingturned on. When changing from AM to MM, the liquid crystal displaydevice 1 changes to MM through WMM. When changing from MM to AM, theliquid crystal display device 1 changes to AM through WMA. To updatedisplay content in MM, the liquid crystal display device 1 changes fromMM through WMM back to MM.

FIG. 7 is a diagram illustrating an operation state of each component ofthe pixel drive circuit 50 and the MIP circuit 60 before the liquidcrystal display device 1 changes to WMA or WMM after being turned on. InFIG. 7, for example, an input side of the signal line DTL is denoted by“Sig”, an input side of the first scanning line SCL is denoted by“Gate”, an input side of the counter electrode 45 is denoted by “CS”, aninput side of the wire VRAM is denoted by “VRAM”, an input side of thewire VSS is denoted by “VSS”, and an input side of the second scanningline SCLM is denoted by “GateM”. FIG. 8 is a timing chart schematicallyillustrating the potentials of the signal line DTL, the counterelectrode 45, the first scanning line SCL, the second scanning lineSCLM, and the wire VRAM before the liquid crystal display device 1changes to WMA or WMM after being turned on. Before the liquid crystaldisplay device 1 changes to WMA or WMM after being turned on, thepotential of the wire VRAM is at the VGH potential. Simultaneously, thepotential of the second scanning line SCLM is at the potential (VGHpotential) of the latch update signal, and the TFT 81 is turned on. TheMIP circuit 60 in this state is at Low. Accordingly, the TFT 71 isturned on, whereas the TFT 72 is turned off. Before the liquid crystaldisplay device 1 changes to WMA or WMM after being turned on, thepotential of the first scanning line SCL is at the VGH potential.Accordingly, the TFT 51 is turned on. The signal line DTL is suppliedwith no signal and thus is at the GND potential. The potential of thecounter electrode 45 is at the GND potential. Accordingly, voltageapplied to the liquid crystal layer 43 is zero, and thus the displayregion of the pixel 49 is turned off.

FIG. 9 is a diagram illustrating the operation state of each componentof the pixel drive circuit 50 and the MIP circuit 60 in WMA. FIG. 10 isa timing chart schematically illustrating the potentials of the signalline DTL, the counter electrode 45, the first scanning line SCL, thesecond scanning line SCLM, and the wire VRAM in WMA. In the case of WMA,the potential of the counter electrode 45 is at the GND potential. Thepotential of the first scanning line SCL is at a VGL potential. The VGLpotential is lower than the VGH potential. In this case, the TET 51 isturned off. The display region in this state is in a display state(Previous Display Mode: PDM) at mode change. The display region in thedisplay state (PDM) at mode change is in a non-transmission state(black). The simple notation of “1H” indicates “one horizontal scanningduration”. One horizontal scanning duration is the duration of signalinput to the pixels 49 in a predetermined number of pixel rows. Thepredetermined number is optional and can be set as appropriate, assumingthe pixel rows of the pixels 49 included in the display unit 10 aredriven in a divided manner.

In the case of WMA, the second scanning line SCLM is supplied with thelatch update signal. The latch update signal is supplied to scan theentire display region of the display unit 10 in units of pixel rows inthe vertical direction (pixel column direction). In other words, thelatch update signal is supplied in each 1H to drive the TFT 81 coupledwith the MIP circuit 60 of a pixel in a different pixel row. In FIG. 9,for example, “active” represents the state of a target of signal supplycorresponding to such scanning in the vertical direction. In FIG. 9, thesecond scanning line SCLM and the TFT 81 are active. When the TFT 81 isactive in WMA, the potential of the wire VRAM is at the VDD potential.When the potential of the wire VRAM is at the VDD potential, the MIPcircuit 60 becomes a state (High or Low) in accordance with thepotential of a signal input from the signal line DTL when the TFT 81 isturned on. In the case of WMA, the potential of the signal line DTL isat the GND potential and lower than the potential (VDD) of the wireVRAM. Accordingly, the MIP circuit 60 becomes Low irrespective of itsprevious state. In other words, at the timing of WMA, the MIP circuits60 of all pixels become Low.

FIG. 11 is a diagram illustrating the operation state of each componentof the pixel drive circuit 50 and the MIP circuit 60 in AM. FIG. 12 is atiming chart schematically illustrating the potentials of the signalline DTL, the counter electrode 45, the first scanning line SCL, thesecond scanning line SCLM, and the wire VRAM in AM. In the case of AM,the first scanning line SCL is supplied with a drive signal to scan theentire display region of the display unit 10 in units of pixel rows inthe vertical direction (pixel column direction). The signal line DTL issupplied with the gradation signal in accordance with the gradationvalue of each pixel 49. In other words, in the case of AM, the displayregion of the pixel 49 performs the multiple gradation outputting inaccordance with a gradation value indicated by the gradation signal.Accordingly, in the case of AM, the pixel 49 is driven to performdisplay output in accordance with the gradation signal generated basedon image data. In the case of AM, the potential of the wire VRAM is atthe VGH potential. Simultaneously, the potential of the second scanningline SCLM is at the VGL potential, and the TFT 81 is turned off. At suchpotentials of the wire VRAM and the second scanning line SCLM, thesetting of the MIP circuit 60 is maintained. The MIP circuit 60 is setto Low at the timing of WMA, and thus the MIP circuit 60 is maintainedat Low during an operation in AM.

In the case of AM, as illustrated in FIG. 12, the inversion drive isperformed in, for example, each 1H. Specifically, the sign of potentialis inverted in accordance with the potential of the gradation signalsupplied to the pixel drive circuit 50 through the signal line DTL and adrive voltage (VCOM) of the counter electrode 45.

FIG. 13 is a diagram illustrating the operation state of each componentof the pixel drive circuit 50 and the MIP circuit 60 in WMM. FIG. 14 isa timing chart schematically illustrating the potentials of the signalline DTL, the counter electrode 45, the first scanning line SCL, thesecond scanning line SCLM, and the wire VRAM in WMM. In the case of WMM,similarly to the case of WMA, the display region becomes the displaystate (PDM) at mode change. In the case of WMM, similarly to the case ofWMA, the second scanning line SCLM and the TFT 81 become active, and thepotential of the wire VRAM becomes equal to the VDD potential. In thecase of WMM, however, unlike the case of WMA, a one-bit signal is inputfrom the signal line DTL. This one-bit signal (digital signal) has twopotentials. One (the VGH potential) of the two potentials of the signalis higher than the VDD potential, whereas the other (the GND potential)is lower than the VDD potential. In the case of the potential higherthan the VDD potential, the MIP circuit 60 becomes High. In the case ofthe potential lower than the VDD potential, the MIP circuit 60 becomesLow. In other words, the MIP circuit 60 is set to High or Low at thetiming of WMM. Whether the MIP circuit 60 of each pixel is set to Highor Low at the timing of WMM depends on a value that the digital signaltransmitted through the signal line DTL indicates.

In this manner, the memory (MIP circuit 60) is coupled with wire (thewire VRAM) at a predetermined middle potential (the voltage of the VDDpotential). The one-bit signal is input to the memory as a signalindicating two values by high and low potentials with respect to thismiddle potential.

FIG. 15 is a diagram illustrating the operation state of each componentof the pixel drive circuit 50 and the MIP circuit 60 in MM. FIG. 16 is atiming chart schematically illustrating the potentials of the signalline DTL, the counter electrode 45, the first scanning line SCL, thesecond scanning line SCLM, and the wire VRAM in MM. In the case of MM,the potential of the wire VRAM is at the VGH potential, and thepotential of the second scanning line SCLM is at the VGL potential. Inother words, the setting of the MIP circuit 60 is maintained. In thecase of MM, the potential of the first scanning line SCL is at the VGHpotential. Accordingly, the TFT 51 is turned on. The potential of thesignal line DTL is a potential in accordance with a dedicated signal(xCS) supplied to the signal line DTL in MM. This dedicated signal is,for example, the signal in which the sign of the drive voltage (VCOM)supplied to the counter electrode 45 in the case of MM is inverted. Inthe case of MM, the inversion drive is performed. Specifically, the signof the signal is inverted in, for example, each one frame (60 Hz).

In the case of MM, turning ON and OFF of the TFTs 71 and 72 depends onthe setting of the MIP circuit 60 performed at the timing of WMM. Whenthe MIP circuit 60 is Low, the TFT 71 is turned on and the TFT 72 isturned off. In other words, when the MIP circuit 60 is Low, the couplewire is coupled with the signal line DTL, so that the potential of thepixel electrode 44 is a potential in accordance with a signal throughthe signal line DTL. The potential of the counter electrode 45 in thecase of MM is a potential with a sign opposite to the sign of thepotential of the pixel electrode 44. Thus, when the MIP circuit 60 isLow, voltage is applied to the liquid crystal layer 43. In the firstembodiment, when the MIP circuit 60 is Low in the case of MM, thepotentials of the dedicated signal (xCS) and the drive voltage (VCOM)are set so as to turn on the display region of the pixel 49. Incontrast, when the MIP circuit 60 is High, the TFT 72 is turned on, andthe TFT 71 is turned off. In other words, when the MIP circuit 60 isHigh, the couple wire is coupled with the counter electrode 45. In thiscase, the pixel electrode 44 and the counter electrode 45 have identicalpotentials. Thus, when the MIP circuit 60 is High, the voltage appliedto the liquid crystals is zero, and thus the display region of the pixel49 is turned off. In this manner, in the case of MM, the pixel 49 isdriven to perform display output in accordance with the one-bit signal(High or Low) stored in the memory (MIP circuit 60).

As described above, the signal line DTL included in the display unit 10transmits the one-bit signal to be set to the gradation signal and thememory. The first scanning line SCL included in the display unit 10turns on and off the TFT 51 by transmitting a first scanning signal(drive signal) indicating whether to couple the pixel drive circuit 50and the signal line DTL. The second scanning line SCLM included in thedisplay unit 10 transmits a second scanning signal (the latch updatesignal) indicating whether to couple the memory (MIP circuit 60) and thesignal line DTL.

The pixel drive circuit 50 controls the display state (gradation) of thedisplay region by applying, to the liquid crystals, voltage due to apotential difference with respect to a reference electrode (the counterelectrode 45) of a reference potential (VCOM) having a periodicallyinverting sign. The memory (MIP circuit 60) includes a first switch (TFT71) for switching coupling and non-coupling between the pixel drivecircuit 50 and the signal line DTL, and a second switch (the TFT 72) forswitching coupling and non-coupling between the pixel drive circuit 50and the reference electrode. The control unit 20 outputs the gradationsignal to the signal line DTL when the pixel 49 operates in the firstmode (AM), and outputs, to the signal line DTL, the memory settingsignal (xCS) of a potential different from the reference potential(VCOM) when the pixel 49 operates in the second mode (MM). Accordingly,when the pixel 49 operates in the first mode or when voltage is appliedto the liquid crystals in the display region of the pixel 49 operatingin the second mode, the control unit 20 couples the pixel drive circuit50 and the signal line DTL and does not couple the pixel drive circuit50 and the reference electrode. When voltage is not effectively appliedto the liquid crystals in the display region of the pixel 49 operatingin the second mode, the control unit 20 does not couple the pixel drivecircuit 50 and the signal line DTL and couples the pixel drive circuit50 and the reference electrode. The description of “voltage is noteffectively applied” refers to a situation in which no voltage isapplied because no potential difference is generated between the pixelelectrode 44 and the reference electrode when the potential of the pixelelectrode 44 is equal to the potential of the reference electrode(counter electrode 45).

The control unit 20 performs signal output for operating each pixel 49of the display unit 10 in each mode described with reference to FIGS. 7to 16, and processing for the signal output. Specifically, in the casesof WMA and WMM, the control unit 20 performs processing for setting thesecond scanning line SCLM and the TFT 81 to be active and setting thepotential of the wire VRAM to be the VDD potential. In the case of WMA,the control unit 20 performs processing for setting the signal line DTLto be the GND potential without outputting a signal thereto. In the caseof WMM, the control unit 20 performs processing for outputting, to thesignal line DTL, the one-bit signal in accordance with the turning onand off of each pixel 49. In the cases of AM and MM, the control unit 20performs processing for maintaining the one-bit signal (High or Low) setto the MIP circuit 60 by setting the potential of the wire VRAM to bethe VGH potential and setting the potential of the second scanning lineSCLM to be the VGL potential. In the case of AM, the control unit 20generates the gradation signal for each pixel 49 based on an imagesignal and outputs the gradation signal to the pixel 49 through thesignal line DTL coupled the pixel 49. In the case of MM, the controlunit 20 generates the one-bit signal to be set to the MIP circuit 60 ofeach pixel 49 of the display unit 10 based on an image signal, andoutputs the one-bit signal to the pixel 49 through the signal line DTLcoupled with the pixel 49.

Through the above-described processing, the control unit 20 outputs thefirst scanning signal (drive signal) and the second scanning signal (thelatch update signal) not to couple the pixel drive circuit 50 and thesignal line DTL in a first duration (WMA duration) and a third duration(WMM duration) but to couple the memory (MIP circuit 60) and the signalline DTL, and thus sets the memory to be a non-operational state (Low)in the first duration, and writes the one-bit signal to the memory inthe third duration.

Part of the processing in accordance with each mode by the control unit20 is performed through signal output to the X driver 32 and the Ydriver 31 which are circuits provided to the display unit 10.Specifically, for example, as illustrated in FIG. 5, the first scanningline SCL, the counter electrode 45, and the second scanning line SCLMare coupled with the X driver 32. The control unit 20 performs, usingthe X driver 32, signal output through the first scanning line SCL, thecounter electrode 45, and the second scanning line SCLM in each mode.The signal line DTL is coupled with the Y driver 31. The control unit 20performs, using the Y driver 31, signal output through the signal lineDTL in each mode.

In the first embodiment, the wire VRAM and the wire VSS are directlycoupled with the control unit 20, but the MIP circuit 60 may becontrolled through a dedicated circuit for signal output to the MIPcircuit 60 provided independently from the control unit 20.

Switching between the modes is performed by the control device coupledthrough the FPC. The control device outputs the mode specifying signalfor specifying the mode of the liquid crystal display device 1. Thecontrol unit 20 operates the display unit 10 in any one of AM and MM inaccordance with the mode indicated by this mode specifying signal. Thecontrol unit 20 performs processing related to WMA in advance when themode changes to AM, and performs processing related to WMM in advancewhen the mode changes to MM. When the control device outputs the modespecifying signal which indicates update of display content duringoperation in MM, the control unit 20 updates the display content in MMthrough WMM.

FIGS. 17, 18, and 19 are each a timing chart illustrating a relationamong the mode of the liquid crystal display device 1, a signal outputto the signal line DTL, a signal output to the counter electrode 45, andwhether to perform display output by the display unit 10 in the firstembodiment.

For example, as illustrated in FIG. 17, when MM is the setting (start-upsetting) of the mode at start-up of the liquid crystal display device 1,the control unit 20 performs the processing related to WMM in the first1F after the liquid crystal display device 1 is turned on. During the 1Fin which the processing related to WMM is performed, the signal line DTLis active as described above. The potential of the counter electrode 45is equal to a potential (the GND potential) of the display state (PDM)at mode change. During a time until the liquid crystal display device 1is turned on or during WMM, the pixel 49 is in the non-transmissivestate.

After the 1F in which the processing related to WMM is performed, thecontrol unit 20 performs processing related to display in MM.Accordingly, the potential of the signal line DTL and the potential ofthe counter electrode 45 are inverted in each 1F with their signs beingopposite to each other.

As illustrated in FIG. 18, when the start-up setting is AM, the controlunit 20 performs the processing related to WMA in the first 1F after theliquid crystal display device 1 is turned on. During the 1F in which theprocessing related to WMA is performed, the potential of the signal lineDTL and the potential of the counter electrode 45 are equal to apotential (the GND potential) of the display state at mode change.

After the 1F in which the processing related to WMA is performed, thecontrol unit 20 performs processing related to display in AM.Accordingly, the potential of the signal line DTL and the potential ofthe counter electrode 45 are inverted in each 1H with their signs beingopposite to each other.

As illustrated in FIG. 19, when the mode changes from AM to MM, thecontrol unit 20 performs the processing related to WMM in 1F durationsbefore and after the change. When display content is modified in MMwhile the mode is maintained, the control unit 20 performs theprocessing related to WMM in 1F durations the modification of thedisplay content before and after. When the mode changes from MM to AM,the control unit 20 performs the processing related to WMA in 1Fdurations before and after the change.

In this manner, the control unit 20 performs switching between the firstmode (AM) causing the display unit 10 to perform display output inaccordance with the gradation signal which is generated based on imagedata, and the second mode (MM) causing the display unit 10 to performdisplay output in accordance with the one-bit signal which is stored inthe memory (MIP circuit 60). In the liquid crystal display device 1,signals are input to the pixel 49 in the first duration (WMA duration)in which a signal for setting the memory to be the non-operational state(Low) is output when the pixel 49 operates in the first mode (AM), asecond duration (AM duration) in which the gradation signal is output tothe pixel drive circuit 50 when the pixel 49 operates in the first mode,and the third duration (WMM duration) in which the one-bit signal isoutput to the memory when the pixel 49 operates in the second mode.

Although the period of sign inversion of a signal through the inversiondrive in AM and MM is optional, the period of the inversion drive in thecase of MM is longer than the period of the inversion drive in the caseof AM. A longer period of the inversion drive leads to reduced electricpower consumption in display output. In the case of MM, display outputcan be performed without outputting the gradation signal to each pixel49 in each frame, and thus electric power consumption can be reduced ascompared to the case of AM.

FIG. 20 is a timing chart illustrating an exemplary potential change inresponse to signal output related to one unit pixel in 1H duration inWMA. FIG. 21 is a timing chart illustrating an exemplary potentialchange in response to signal output related to one unit pixel in 1Hduration in AM. FIG. 22 is a timing chart illustrating an exemplarypotential change in response to signal output related to one unit pixelin 1H duration in WMM. In 1H duration of WMA, AM, and WMM, signals fordriving switches are output to sequentially turn on and off switches(ASW1, ASW2, and ASW3) for transmitting a signal from the signal lineDTL to any one of three sub pixels included in one unit pixel.

In WMA, the control unit 20 performs signal output in processing forsetting the MIP circuit 60 to be Low. Accordingly, the potential of thefirst scanning line SCL (Gate) becomes equal to the VGL potential, thesecond scanning line SCLM (GateM) becomes active, and the potential ofthe signal line DTL becomes equal to the GND potential.

In AM, the control unit 20 performs signal output in processing forperforming the multiple gradation outputting through the gradationsignal. Accordingly, the first scanning line SCL (Gate) becomes active,and the potential of the signal line DTL becomes equal to a potential inaccordance with a signal indicating the gradation value of each of thethree sub pixels (RGB). In AM, the MIP circuit 60 is maintained to beLow, and thus the potential of the second scanning line SCLM (GateM)becomes equal to the VGL potential.

In WMM, the control unit 20 performs signal output in processing forsetting the MIP circuit 60 to be High or Low. Accordingly, the potentialof the first scanning line SCL (Gate) becomes equal to the VGLpotential, and the second scanning line SCLM (GateM) becomes active. Inthe first embodiment, one sub pixel outputs gradation values in threebits as described with reference to FIG. 4, and thus a signaltransmitted through the signal line DTL is a signal corresponding toinformation in three bits. More specifically, a one-bit signal istransmitted to each of the three pixels 49 included in one sub pixel,and thus, a signal in 1 [bit] [times] 3=3 [bits] is output to one subpixel.

FIG. 23 is a timing chart illustrating an exemplary potential change inresponse to signal output related to one unit pixel in 1H duration inMM. In MM, the control unit 20 does not update display content of thepixel 49. Accordingly, the switches (ASW1, ASW2, and ASW3) fortransmitting a signal from the signal line DTL to any one of the threesub pixels included in one unit pixel are maintained to be off.Simultaneously, the potential of the first scanning line SCL (Gate)becomes equal to the VGH potential, and the potential of the signal lineDTL becomes a potential in accordance with the dedicated signal (xCS)supplied to the signal line DTL in MM. In MM, the MIP circuit 60 ismaintained in a state (High or Low) set in the WMM duration, and thusthe potential of the second scanning line SCLM (GateM) becomes equal tothe VGL potential.

As described above, according to the first embodiment, the liquidcrystal display device 1 includes the display unit 10 including thepixels 49 arranged in the row and column directions, each pixel 49including the pixel drive circuit 50 configured to apply voltage to theliquid crystals in the display region configured to transmit light inaccordance with voltage applied to the liquid crystals and the memory(MIP circuit 60) configured to store therein the one-bit signalindicating whether to apply voltage to the liquid crystals in thedisplay region, and the control unit 20 configured to perform switchingbetween the first mode (AM) causing the display unit 10 to performdisplay output in accordance with the gradation signal which isgenerated based on image data, and the second mode (MM) causing thedisplay unit 10 to perform display output in accordance with the one-bitsignal which is stored in the memory. This configuration achieves bothof a display output function having gradation capability at more thantwo values in the first mode, and a memory function in the second mode.Switching can be performed between display output using the memoryfunction in the second mode, and display output with the gradationcapability at more than two values in the first mode.

Signals are input to the pixel 49 in the first duration (WMA duration)in which a signal for setting the memory to be the non-operational stateis output when the pixel operates in the first mode, the second duration(AM duration) in which the gradation signal is output to the pixel drivecircuit 50 when the pixel operates in the first mode, and the thirdduration (the WMM duration) in which the one-bit signal is output to thememory when the pixel 49 operates in the second mode. With thisconfiguration, a change is made to the second duration through the firstduration, which allows the display unit 10 operated in the second modeto change to the first mode. The display unit 10 operated in the firstmode can be changed to the second mode through the third duration.

The display unit 10 includes the signal line DTL for transmitting thegradation signal and the one-bit signal, the first scanning line SCL fortransmitting the first scanning signal (drive signal) which indicateswhether to couple the pixel drive circuit 50 and the signal line DTL,and the second scanning line SCLM for transmitting the second scanningsignal (the latch update signal) which indicates whether to couple thememory and the signal line DTL. With this configuration, selective useof the first scanning signal and the second scanning signal allows thetransmission of the gradation signal to the pixel drive circuit 50 andthe transmission of the one-bit signal to the memory to be performedthrough the signal line DTL in common.

The control unit 20 does not couple the pixel drive circuit 50 and thesignal line DTL but couples the memory and the signal line DTL in thefirst duration and the third duration. The control unit 20 sets thememory to be the non-operational state in the first duration, and writesthe one-bit signal to the memory in the third duration. In this manner,switching can be performed between the states of the memory in the firstmode and the second mode.

The memory is coupled with wire (the wire VRAM) of the predeterminedmiddle potential, and the one-bit signal is input to the memory as asignal indicating two values by high and low potentials with respect tothe middle potential. This configuration allows the transmission of theone-bit signal to the memory to be performed by a simple method.

The pixel drive circuit 50 applies, to the liquid crystals, voltage dueto a potential difference with respect to the reference electrode (thecounter electrode 45) of the reference potential (VCOM) with aperiodically inverting sign. The memory (MIP circuit 60) includes thefirst switch (TFT 71) for switching coupling and non-coupling betweenthe pixel drive circuit 50 and the signal line DTL, and the secondswitch (the TFT 72) for switching coupling and non-coupling between thepixel drive circuit 50 and the reference electrode. The control unit 20outputs the gradation signal to the signal line DTL when the pixel 49operates in the first mode (AM), and outputs the memory setting signal(xCS) of a potential different from the reference potential (VCOM) tothe signal line DTL when the pixel 49 operates in the second mode (MM).The control unit 20 couples the pixel drive circuit 50 and the signalline DTL but does not couple the pixel drive circuit 50 and thereference electrode when the pixel 49 operates in the first mode or whenvoltage is applied to the liquid crystals in the display region of thepixel 49 operating in the second mode. The control unit 20 does notcouple the pixel drive circuit 50 and the signal line DTL but couplesthe pixel drive circuit 50 and the reference electrode when no voltageis applied the liquid crystals in the display region of the pixel 49operating in the second mode. In this manner, a mechanism that voltageapplied to the liquid crystals can be switched between the first modeand the second mode allows switching between the multiple gradationoutputting in the first mode, and outputting through the turning on andoff of the pixel 49 in the second mode.

Second Embodiment

The following describes a second embodiment of the present invention.Any configuration same as that in the first embodiment is denoted by thesame reference numerals and symbols, and description thereof will beomitted in some cases. In the second embodiment, one horizontal scanningduration (1H) includes a duration that can be used as the first duration(WMA duration), the second duration (AM duration), and the thirdduration (WMM duration). When switching is performed between the firstmode (AM) and the second mode (MM), one horizontal scanning durationincludes at least one of a duration in which the first duration (WMAduration) and the second duration (AM duration) are continuous, or aduration in which the second duration (AM duration) and the thirdduration (WMM duration) are continuous. In the first duration (WMAduration) and the third duration (WMM duration), no gradation signal isoutput to the pixel drive circuit 50. The specific configuration(hardware) of a liquid crystal display device according to the secondembodiment is the same as that in the first embodiment.

FIG. 24 is a schematic diagram illustrating an exemplary setting ofdurations that are included in 1H and can be used as WMA, AM, and WMM.In the description of the second embodiment, “WMA correspondingduration” refers to a duration used for processing related to the firstduration (WMA duration), “AM corresponding duration” refers to aduration used for processing related to the second duration (AMduration), and “WMM corresponding duration” refers to a duration usedfor processing related to the third duration (WMM duration). Asillustrated in FIG. 24, in the second embodiment, the WMA correspondingduration, the order of the AM corresponding duration, and the WMMcorresponding duration is set to be continuous in 1H duration. Thecontrol unit 20 according to the second embodiment performs processingcorresponding to these durations in 1H duration depending on a mode.Specifically, the control unit 20 according to the second embodimentperforms, in the WMA corresponding duration, the signal output in WMAdescribed with reference to, for example, FIG. 20 in the firstembodiment. The control unit 20 according to the second embodimentperforms, in the AM corresponding duration, the signal output in AMdescribed with reference to, for example, FIG. 21 in the firstembodiment. The control unit 20 according to the second embodimentperforms, in the WMM corresponding duration, the signal output in WMMdescribed with reference to, for example, FIG. 22 in the firstembodiment.

FIG. 24 illustrates signal output possibilities that can be included in1H duration with regard to the second embodiment, but not indicatingthat all signal outputs in WMA, AM, and WMM are continuous in 1Hduration with regard to the first embodiment. In the following, signaloutput patterns in 1H duration with regard to the second embodiment areexemplarily described with reference to FIGS. 25 to 28.

FIG. 25 is a timing chart illustrating exemplary signal output of 1H inthe first frame during an AM operation. Resetting of the MIP circuit 60is performed in the first frame during the AM operation before start ofthe multiple gradation outputting, and thus, in the WMA correspondingduration, the control unit 20 performs the signal output in WMA, inother words, signal output related to processing of setting the MIPcircuit 60 to be Low. In the AM corresponding duration in the 1Hduration which is the same as the duration in which the MIP circuit 60is set to be Low, the control unit 20 performs outputting of signals(signals to the first scanning line SCL and the switches ASW1, ASW2, andASW3) for causing each sub pixel to perform outputting of the gradationsignal generated based on an image signal of the first frame andoutputting in accordance with this gradation signal. In other words,right before the AM corresponding duration in the first frame, thecontrol unit 20 performs the processing related to WMA for modeswitching in the 1H duration including the AM corresponding duration inthis first frame.

FIG. 26 is a timing chart illustrating exemplary signal output of 1H inthe second frame or later during the AM operation. In the second frameor later during the AM operation, the control unit 20 does not performsignal output in the WMA corresponding duration, but performs signaloutput for the multiple gradation outputting in the AM correspondingduration.

As illustrated in FIGS. 25 and 26, in the AM operation in which the modedoes not change to MM, the control unit 20 does not perform signaloutput in the WMM corresponding duration.

FIG. 27 is a timing chart illustrating exemplary signal output of 1H inthe first frame during a MM operation. In the first frame during the MMoperation, the setting (High or Low) of the MIP circuit 60 is performedbefore one-bit outputting by each pixel 49 and three-bit outputting byeach sub pixel, and thus, in the WMM corresponding duration, the controlunit 20 performs the signal output in WMM, in other words, signal outputrelated to the setting of the MIP circuit 60. FIG. 27 illustrates atiming chart when the mode changes to MM after start of the AMoperation. When the start-up setting is MM, in FIG. 27, no signal outputis performed in the AM corresponding duration.

FIG. 28 is a timing chart illustrating exemplary signal output of 1H inthe second frame or later during the MM operation. In the second frameor later during the MM operation, the setting and resetting of the MIPcircuit 60 are not needed, and thus the control unit 20 does not performsignal output in the WMA corresponding duration and the WMMcorresponding duration. The dedicated signal (xCS) supplied to thesignal line DTL during the MM operation is supplied continuously in 1Hduration including the WMA corresponding duration and the WMMcorresponding duration. When switching of display content is performedin the MM operation while the mode is maintained, the control unit 20outputs, in the WMM corresponding duration of the timing chartillustrated in FIG. 28, a signal same as a signal in the WMMcorresponding duration illustrated in FIG. 27.

FIG. 29 is a diagram illustrating the process of a mode change of theliquid crystal display device in the second embodiment. In the secondembodiment, 1H duration includes the WMA corresponding duration and theWMM corresponding duration, and thus the processing in WMA and WMMperformed through 1F duration in the first embodiment may be omitted.Accordingly, as illustrated in FIG. 29, the change between AM and MM andthe switching of display content in MM can be performed in each 1F.

As described above, according to the second embodiment, one horizontalscanning duration as the duration of signal input to the predeterminednumber of pixel rows includes a duration that can be used as the firstduration, the second duration, and the third duration. Accordingly,without spending 1F duration to perform WMA and WMM, the change betweenAM and MM and the switching of display content in MM can be performed ineach 1F. Thus, the mode switching between AM and MM and the switching ofdisplay content in MM can be performed faster.

Third Embodiment

The following describes a third embodiment of the present invention. Anyconfiguration same as those in the first and the second embodiments isdenoted by the same reference numerals and symbols, and descriptionthereof will be omitted in some cases.

FIG. 30 is a schematic diagram illustrating an exemplary laminatedstructure of a liquid crystal display device according to the thirdembodiment. The liquid crystal display device according to the thirdembodiment includes, in addition to the configuration in the secondembodiment, a touch panel 90 serving as a touch detecting unitconfigured to detect a touch operation on the display surface of thedisplay unit 10. Any component of the liquid crystal display device inthe third embodiment is the same as that in the first embodiment exceptfor the touch panel 90.

FIG. 31 is an exploded perspective view illustrating an exemplary mainconfiguration of the touch panel 90. The touch panel 90 includes a touchdetection electrode TDL and a touch detection drive electrode COMt. Alayer in which the touch detection electrode TDL is provided and a layerin which the touch detection drive electrode COMt is provided areprovided so as not be in contact with each other at a predetermineddistance therebetween. The touch detection electrode TDL and the touchdetection drive electrode COMt have longitudinal directions differentfrom each other, and have a twisted positional relation.

At operation of the touch panel 90, in other words, at the time at whichtouch detection is performed by the touch panel 90, the control unit 20outputs a touch detection drive signal Vcomt to the touch detectiondrive electrode COMt. Capacitance is generated between the touchdetection electrode TDL and the touch detection drive electrode COMt inresponse to the outputting of the drive signal Vcomt. When an objectsuch as a finger F becomes adjacent or contact to the display surface onwhich the touch panel 90 is provided, this capacitance changes. Thecontrol unit 20 performs touch detection by detecting this capacitancechange as a touch detection signal Vdet.

A plurality of the touch detection electrodes TDL and the touchdetection drive electrodes COMt are provided. The control unit 20performs a scanning operation (Scan) to output the drive signal Vcomt onthe touch detection drive electrodes COMt in parallel at differenttimings. Based on the touch detection drive electrode COMt to which thedrive signal Vcomt is output, and the touch detection electrode TDL bywhich the touch detection signal Vdet is detected at the timing of thedrive signal Vcomt output, a position where the object is adjacent orcontact to the display surface is determined.

The touch panel 90 described with reference to FIGS. 30 and 31 isprovided separately from the display unit 10, but an in-cell touch panelliquid crystal display, in which the display unit 10 and the touch panel90 are integrated with each other, is applicable. A touch detectionmethod is not limited to the specific configuration of the touch panel90. For example, what is called a self matrix method is applicable inwhich signal detection is performed by applying drive voltage to each ofelectrodes arranged in a matrix. In this case, the same electrodecorresponds to the touch detection electrode TDL and the touch detectiondrive electrode COMt in the touch panel 90. In another method in touchdetection, tiled electrodes are provided in the row and columndirections and coupled with each other through bridge wiring in the rowand column directions so as to achieve a single layer type that thetouch detection electrode TDL and the touch detection drive electrodeCOMt are formed in an identical layer.

A touch detection duration in which detection of a touch operation isperformed by the touch panel 90 in the third embodiment is a duration inwhich no signal transmission is performed through the first scanningline SCL and the second scanning line SCLM. The following describesrelation between the touch detection duration and a signal output timingin each mode with reference to FIGS. 32 to 36. The touch detectionduration in FIG. 32 to FIG. 36 is “ON” duration in “TPScan”. The touchdetection duration is a duration in which the touch detection drivesignal Vcomt described above is output.

FIG. 32 is a timing chart illustrating an exemplary relation betweensignal output and the touch detection duration of 1H in the first frameduring the AM operation. As described with reference to FIG. 25 in thesecond embodiment, in the AM operation in which the mode does not changeto MM, the control unit 20 does not perform signal output in the WMMcorresponding duration. Thus, in the first frame during the AMoperation, the touch detection duration can be set to be in the WMMcorresponding duration, and thus signal output related to the displayoutput by the display unit 10 and the touch detection by the touch panel90 can be performed at different timings.

When the touch detection is performed simultaneously at a timing atwhich the signal output related to the display output by the displayunit 10 is performed, noise occurring in the signal output related tothe display output by the display unit 10 is likely to affect theaccuracy of the touch detection through its influence on the capacitanceof the touch panel 90. The signal output related to the display outputby the display unit 10 and the touch detection by the touch panel 90 areperformed at different timings, and thus the influence of external noisein the touch detection can be reduced.

As illustrated in FIG. 32, the first frame during the AM operationincludes a duration in which no signal output is performed until the AMcorresponding duration starts after the timing of signal output in theWMA corresponding duration. Thus, the touch detection duration may beset also in this duration.

FIG. 33 is a timing chart illustrating an exemplary relation betweensignal output and the touch detection duration of 1H in the second frameor later during the AM operation. As described with reference to FIG. 26in the second embodiment, in the second frame or later during the AMoperation, the control unit 20 does not perform signal output in the WMAcorresponding duration and the WMM corresponding duration. Thus, in thesecond frame or later during the AM operation, the touch detectionduration can be set to be in the WMA corresponding duration and the WMMcorresponding duration, and thus the signal output related to thedisplay output by the display unit 10 and the touch detection by thetouch panel 90 can be performed at different timings.

FIG. 34 is a timing chart illustrating an exemplary relation betweensignal output and the touch detection duration of 1H in the first frameduring the MM operation. As described with reference to FIG. 27 in thesecond embodiment, during the MM operation, the control unit 20 does notperform signal output in the WMA corresponding duration. Thus, in thefirst frame during the MM operation, the touch detection duration can beset to be in the WMA corresponding duration, and thus the signal outputrelated to the display output by the display unit 10 and the touchdetection by the touch panel 90 can be performed at different timings.

As illustrated in FIG. 34, the first frame during the MM operationincludes a duration in which no signal output is performed until the WMAcorresponding duration in the next frame starts after the timing ofsignal output in the WMM corresponding duration. Thus, the touchdetection duration may be set also in this duration.

FIG. 35 is a timing chart illustrating an exemplary relation betweensignal output and the touch detection duration of 1H in the second frameor later during the MM operation. As described in the first embodiment,during the MM operation, the potential of the signal line DTL and thepotential of the counter electrode 45 are inverted in each frame. Inthis case, the control unit 20 does not perform individual signal outputto each pixel 49. Accordingly, in the second frame during the MMoperation, the WMA corresponding duration, the AM correspondingduration, and the WMM corresponding duration can be used as the touchdetection duration.

FIG. 32 to FIG. 35 illustrate the examples in which different touchdetection durations are set in the first frame during the AM operation,the second frame or later during the AM operation, the first frameduring the MM operation, and the second frame or later during the MMoperation. However, the same rule may be applied to set touch detectiondurations in part or all of these frames.

FIG. 36 is a diagram illustrating another exemplary relation amongdurations that are included in 1H and can be used as WMA, AM, and WMM,and the touch detection duration. In any of the first frame during theAM operation, the second frame or later during the AM operation, thefirst frame during the MM operation, the second frame or later duringthe MM operation, the control unit 20 performs no signal output to eachpixel 49 in a duration until the AM corresponding duration starts afterthe timing of signal output in the WMA corresponding duration, and in aduration until the WMA corresponding duration in the next frame startsafter the timing of signal output in the WMM corresponding duration.Thus, as illustrated in FIG. 36, touch detection durations are set to bethe duration until the AM corresponding duration starts after the timingof signal output in the WMA corresponding duration, and the WMAcorresponding duration in the next frame after the timing of signaloutput in the WMM corresponding duration, and thus, regardless of anytiming of the first frame during the AM operation, the second frame orlater during the AM operation, the first frame during the MM operation,and the second frame or later during the MM operation, the signal outputrelated to the display output by the display unit 10 and the touchdetection duration by the touch panel 90 can be performed at differenttimings.

As described above, according to the third embodiment, no signaltransmission is performed through the first scanning line SCL and thesecond scanning line SCLM in the touch detection duration in which thetouch detecting unit (touch panel 90) performs detection of a touchoperation. This allows reduction in the influence of external noise inthe touch detection, thereby further improving the accuracy of the touchdetection.

It should be understood that the present invention provides any effectother than those achieved by the aspects described in the embodiments,that is clear from description of the present specification or can bethought of by the skilled person in the art as appropriate.

For example, a setting signal is a one-bit signal in the above-describedembodiments, which is exemplary and does not limit the presentinvention. The setting signal may be a signal in two bits or more. Thememory is configured to store therein the amount of information inaccordance with the number of bits of the setting signal.

The characteristics of the present invention can be described asfollows.

(1) A liquid crystal display device including:

a display unit configured to pixels in a display region, a pixel drivecircuit configured to apply voltage to liquid crystals, a memoryconfigured to store therein a setting signal in at least one bitindicating whether to apply voltage to the liquid crystals in thedisplay region, and two switch elements of a first switch and a secondswitch for switching coupling with the pixel drive circuit; and

a controller configured to rewrite the setting signal stored in thememory when a mode in which the display unit is operated is switched,between a first mode causing the display unit to perform display outputin accordance with a gradation signal generated based on image data inthe case of turning on one of the two switch elements, and a second modecausing the display unit to perform display output in accordance with asetting signal stored in the memory in the case of turning on any one ofthe two switch elements.

(2) The liquid crystal display device according to (1), in which

a pixel of the pixels includes a third switch that couples the memoryand a wire through which the setting signal is transmitted, and

the controller is configured to turn on the third switch element torewrite the setting signal stored in the memory when performingswitching between the first mode and the second mode.

(3) The liquid crystal display device according to (1), in which aduration of signal input to a pixel of the pixels is one of a firstduration in which a signal for setting the memory to be anon-operational state is output when the pixel operates in the firstmode, a second duration in which the gradation signal is output to thepixel drive circuit when the pixel operates in the first mode, and athird duration in which the setting signal is output to the memory whenthe pixel operates in the second mode.(4) The liquid crystal display device according to (3), in which onehorizontal scanning duration as a duration of signal input to apredetermined number of pixel rows includes a duration that can be usedas the first duration, the second duration, and the third duration.(5) The liquid crystal display device according to (3), in which, whenswitching is performed between the first mode and the second mode, onehorizontal scanning duration includes at least one of a duration inwhich the first duration and the second duration are continuous or aduration in which the second duration and the third duration arecontinuous.(6) The liquid crystal display device according to (3), in which thegradation signal is not output to the pixel drive circuit in the firstduration and the third duration.(7) The liquid crystal display device according to (1), in which thedisplay unit includes:

a signal line through which the gradation signal and the setting signalare transmitted,

a first scanning line through which a first scanning signal indicatingwhether to couple the pixel drive circuit and the signal line istransmitted, and

a second scanning line through which a second scanning signal indicatingwhether to couple the memory and the signal line is transmitted.

(8) The liquid crystal display device according to (7), furtherincluding a touch detecting unit configured to detect a touch operation,in which no signal transmission is performed through the first scanningline and the second scanning line in a touch detection duration in whichthe touch detecting unit performs the detection of the touch operation.(9) The liquid crystal display device according to (7) or (8), in whichthe controller is configured not to couple the pixel drive circuit andthe signal line but couples the memory and the signal line in the firstduration and the third duration, the controller is configured to set thememory to a non-operational state in the first duration, and thecontroller is configured to write the setting signal to the memory inthe third duration.(10) The liquid crystal display device according to (9), in which

the memory is coupled with a wire at a predetermined middle potential,and

the setting signal is input to the memory as a signal indicating twovalues by high and low potentials with respect to the middle potential.

(11) The liquid crystal display device according to any one of (7) to(10), in which

the pixel drive circuit is configured to apply, to the liquid crystals,voltage due to a potential difference with respect to a referenceelectrode of a reference potential,

the first switch is configured to switch coupling and non-couplingbetween the pixel drive circuit and the signal line,

the second switch is configured to switch coupling and non-couplingbetween the pixel drive circuit and the reference electrode, and

the controller is configured to output the gradation signal to thesignal line when a pixel of the pixels operates in the first mode, tooutput a memory setting signal having a potential different from thereference potential to the signal line when the pixel operates in thesecond mode, the controller is configured to couple the pixel drivecircuit and the signal line but not to couple the pixel drive circuitand the reference electrode when the pixel operates in the first mode orwhen voltage is applied to the liquid crystals of the pixel operating inthe second mode, and the controller is configured not to couple thepixel drive circuit and the signal line but to couple the pixel drivecircuit and the reference electrode when no voltage is applied to theliquid crystals of the pixel operating in the second mode.

(12) The liquid crystal display device according to (11), in which, inthe first mode, the sign of the reference potential is inverted in eachhorizontal scanning duration, and in the second mode, a sign of thereference potential is inverted in one vertical scanning duration.

The characteristics of the present invention can be also described asfollows.

(13) A liquid crystal display device including:

a display unit including a plurality of pixels configured to transmitlight depending on voltage applied to the liquid crystals,

a signal line through which a gradation signal for applying voltagecorresponding to a gradation value of each pixel is transmitted, and

a reference electrode of a predetermined reference potential, in which

each pixel of the plurality of pixels includes:

-   -   a pixel drive circuit configured to apply voltage in accordance        with a potential difference with respect to the reference        potential to the liquid crystals,    -   a first switch configured to switch coupling and non-coupling        between the pixel drive circuit and the signal line,    -   a second switch configured to switch coupling and non-coupling        between the pixel drive circuit and the reference electrode, and    -   a memory configured to store therein a setting signal indicating        whether to apply voltage to the liquid crystals,

one of switch elements of the first switch and the second switch isconfigured to be turned on and the other switch element is configured tobe turned off depending on the setting signal stored in the memory, and

the setting signal is written to the memory before start of a first modein which voltage in accordance with the gradation signal is applied tothe liquid crystals and before start of a second mode in which it isdetermined whether to apply voltage to the liquid crystals depending onthe setting signal.

(14) A liquid crystal display device including:

a display unit including a display region provided with a plurality ofpixels arranged in row and column directions and configured to transmitlight depending on voltage applied to the liquid crystals;

a signal line through which a plurality of kinds of signals aretransmitted; and

a reference electrode of a predetermined reference potential, in which

each pixel includes:

-   -   a pixel drive circuit configured to apply voltage to the liquid        crystals in the display region,    -   a memory configured to store therein the setting signal,    -   a first switch configured to switch coupling and non-coupling        between the pixel drive circuit and the signal line,    -   a second switch configured to switch coupling and non-coupling        between the pixel drive circuit and the reference electrode, and    -   a third switch configured to switch coupling and non-coupling        between the signal line and the memory,

the plurality of kinds of signals include a gradation signal forapplying voltage corresponding to a gradation value of the pixel to theliquid crystals and a setting signal indicating whether to apply voltageto the liquid crystals,

one of switch elements of the first switch and the second switch isturned on and the other switch element is turned off depending on thesetting signal stored in the memory, and

the third switch is turned on to write the setting signal to the memorybefore start of a first mode in which voltage in accordance with thegradation signal is applied to the liquid crystals and before start of asecond mode in which it is determined whether to apply voltage to theliquid crystals depending on the setting signal.

(15) The liquid crystal display device according to (13), furtherincluding a third switch configured to switch coupling and non-couplingbetween the signal line and the memory, in which the third switch isturned on to write the setting signal to the memory before start of thefirst mode and before start of the second mode.(16) The liquid crystal display device according to (13) or (15), inwhich, when switching is performed from the first mode to the secondmode, in one horizontal scanning duration, the gradation signal istransmitted to the pixel drive circuit through the signal line, and thenthe setting signal is transmitted to the memory, so that the firstswitch is turned on and the second switch is turned off.(17) The liquid crystal display device according to (16), in which, whenswitching is performed from the second mode to the first mode, onehorizontal scanning duration includes a duration including a timing atwhich the gradation signal is transmitted to the pixel drive circuitthrough the signal line in the first mode, and a duration in which thesetting signal is transmitted to the memory, so that the first switch isturned on and the second switch is turned off, and the gradation signalis not transmitted to the pixel drive circuit.(18) The liquid crystal display device according to (16) or (17), inwhich, when switching is performed from the first mode to the secondmode, the gradation signal is not transmitted to the pixel drive circuitin the one horizontal scanning duration, in a duration in which thesetting signal is transmitted to the memory, so that the first switch isturned on and the second switch is turned off.

What is claimed is:
 1. A liquid crystal display device comprising:pixels arranged in a display region, at least one of the pixelsincluding a memory configured to store a setting signal, a first switchhaving a first gate, a first source, and a first drain and a secondswitch having a second gate, a second source and a second drain, thememory being coupled to the first gate and the second gate; a signalline coupled to one of the first source and the first drain; and acontroller configured to rewrite the setting signal stored in the memorywhen a display operation mode is switched between a first mode in whichthe first switch is turned on and the pixel performs display output inaccordance with a gradation signal that is generated based on image dataand provided through the first switch and the signal line, and a secondmode in which any of the first or second switches is turned on and thepixel performs display output in accordance with the setting signalstored in the memory.
 2. The liquid crystal display device according toclaim 1, wherein the pixel includes a third switch that couples thememory and a wire through which the setting signal is transmitted, andthe controller is configured to turn on the third switch to rewrite thesetting signal stored in the memory when switching between the firstmode and the second mode.
 3. The liquid crystal display device accordingto claim 1, wherein a duration of signal input to the pixel is one of: afirst duration in which a signal for setting the memory to turn on thefirst switch is output in the first mode; a second duration in which thegradation signal is output to the pixel in the first mode; and a thirdduration in which the setting signal is output to the memory when thepixel operates in the second mode.
 4. The liquid crystal display deviceaccording to claim 3, wherein one horizontal scanning duration as aduration of signal input to predetermined number of pixel rows includesa duration that can be used as the first duration, the second duration,and the third duration.
 5. The liquid crystal display device accordingto claim 3, wherein, when switching is performed between the first modeand the second mode, one horizontal scanning duration includes at leastone of a duration in which the first duration and the second durationare continuous or a duration in which the second duration and the thirdduration are continuous.
 6. The liquid crystal display device accordingto claim 3, wherein the gradation signal is not output to the pixel inthe first duration and the third duration.
 7. The liquid crystal displaydevice according to claim 1, wherein the pixel includes a pixelelectrode, the gradation signal and the setting signal are transmittedthrough the signal line, a first scanning line is configured to transmita first scanning signal indicating whether to couple the pixel electrodeand the signal line, and a second scanning line is configured totransmit a second scanning signal indicating whether to couple thememory and the signal line.
 8. The liquid crystal display deviceaccording to claim 7, further comprising a touch detecting unitconfigured to detect a touch operation, wherein no signal transmissionis performed through the first scanning line and the second scanningline in a touch detection duration in which the touch detecting unitperforms the detection of the touch operation.
 9. The liquid crystaldisplay device according to claim 3, wherein the pixel includes a fourthswitch arranged between the first switch and a pixel electrode, thecontroller is configured to: couple the memory and the signal linewithout turning on the fourth switch to couple the pixel electrode andthe first switch, in the first duration and the third duration; providethe memory with a signal to turn on the first switch in the firstduration; and write the setting signal to the memory in the thirdduration.
 10. The liquid crystal display device according to claim 1,wherein the memory is coupled with a wire at a predetermined middlepotential, and the setting signal is input to the memory as a signalindicating two values by high and low potentials with respect to themiddle potential.
 11. The liquid crystal display device according toclaim 1, further comprising: a pixel electrode; a reference electrodeconfigured to be provided with a reference potential; and a wire,wherein the first switch is configured to switch coupling andnon-coupling between the pixel electrode and the signal line, the secondswitch is configured to switch coupling and non-coupling between thepixel electrode and the wire providing the reference potential, and thecontroller is configured to: output the gradation signal to the signalline in the first mode; output the setting signal to the signal line inthe second mode; couple the pixel electrode and the signal line withoutcoupling the pixel electrode and the wire by turning on the first switchin the first mode or when the pixel is provided with a voltage differentfrom the reference potential in the second mode; and couple the pixelelectrode and the wire without coupling the pixel electrode and thesignal line by turning on the second switch when the pixel is provided avoltage equal to the reference potential in the second mode.
 12. Theliquid crystal display device according to claim 11, wherein, in thefirst mode, a sign of the reference potential is inverted in eachhorizontal scanning duration, and in the second mode, the sign of thereference potential is inverted in each vertical scanning duration. 13.A liquid crystal display device comprising: a pixel electrode; areference electrode configured to be supplied with a predeterminedreference potential; a signal line configured to provide a gradationsignal, a setting signal, and a first signal that is different from thepredetermined reference potential; a wire; a first switch including afirst gate and being configured to switch coupling and non-couplingbetween the pixel electrode and the signal line; a second switchincluding a second gate and being configured to switch coupling andnon-coupling between the pixel electrode and the wire providing thepredetermined reference potential; and a memory coupled to the firstgate and the second gate and configured to store a setting signal,wherein one of the first switch or the second switch is configured to beturned on and the other of the first switch or the second switch isconfigured to be turned off depending on the setting signal stored inthe memory, and the setting signal is written to the memory before astart of a first mode in which the gradation signal is applied to thepixel electrode through the first switch and before a start of a secondmode in which one of the reference potential and the first signal isapplied to the pixel electrode depending on the setting signal.